Beat egg yolks until light. Add condensed milk and 1/2 cup lime juice. Stir until thickened. Pour into pie crust. Make meringue with egg whites. While beating egg whites, add sugar, one tablespoon at a time. Add a few drops of lime juice or cream of tartar. Cover pie with meringue* and bake 350 degrees until brown. Be sure and perforate pie crust with fork before baking. Also watch closely to make sure pie doesn't brown too much. (*Tip: wet knife before cutting into meringue, this cuts much cleaner.)